1. Field of the Invention
The present invention relates to an ultra high-speed wet etching apparatus for performing uniform, high-speed wet etching of a silicon substrate using an etchant containing hydrofluoric acid (HF) and nitric acid (HNO3).
2. Description of the Related Art
In recent years, semiconductor devices driven by a low voltage have been required in terms of energy saving and global popularization of mobile terminal devices. One technical problem in driving a semiconductor device by a low voltage is to decrease the thickness of a silicon substrate for forming a semiconductor device. In the field of power devices, for example, a silicon substrate is required to have a thickness of 50 μm to 100 μm. In a DRAM or flash memory, the memory density is improved by causing an electrode (Through Silicon Via (TSV)) to extend between the upper and back surfaces of a substrate, and forming the memory to have a multi-layer structure. To drive the device by a lower voltage, and increase the memory density, a silicon substrate has been strongly required to have a thickness as small as 20 μm to 30 μm.
A technique of decreasing the thickness of a silicon substrate includes arranging a power device and memory on the front surface of the silicon substrate, mechanically polishes the back surface of the silicon substrate to a predetermined thickness by back grinding using abrasive polishing grains, and then performs wet etching.